EP1005241B1 - Method for communication between a mobile terminal and an accessory - Google Patents

Abstract

The system uses radio transmissions with encoding to activate the vibrator, warning of incoming calls without audible sound. The system for controlling an accessory from a mobile terminal includes a transmission-reception chain (14 - 28) extending from the mobile terminal to establish connection with the base station of a public network. Without need to modify this chain, a signal generator (14) is used. The signal bits used are applied to modulate a pure sinusoidal wave at a transmission carrier frequency (Fk). This signal is detected at the accessory and used to produce a local signal if the received signal passes a simple reception circuit. The circuit may include a pass-band filter and an envelope detector.

Description

The present invention relates to a method of communication between a mobile terminal and an accessory. The accessory in question may be any, typically a vibrator that replaces a ring to alert the wearer of the mobile terminal that it is called, without making a noise, or even a headset microphone. However, the accessory may also be a connection interface with a more complex peripheral element, such as a microcomputer.
The object of the invention is to facilitate this communication while giving it greater transmission capacity.

In the field of mobile terminals the existence is known accessories that can be connected to a mobile terminal or at least with whom we can receive information from of this mobile terminal. Transmissions between the mobile terminal and the accessory can be acoustic or infrared. In this case they ask to be able to practice specific transmitters and receivers arranged in the mobile terminal and the accessory. It is also known that this transmission is radioelectric. The mode of transmission is example set on a frequency of domestic type (27 MHz) or other. With an adapted protocol it is thus possible to solicit and enter into communication with any accessory. However in these case it is necessary to have in the mobile terminal and in the accessory additional, expensive circuits to carry out such communications.

There is also a transmission mode that could seem natural: the radio transmission system with which the mobile terminal exchanges with a base station of a public network to which it can connect. However, the use of such a system has two problems. First, it is important not to interfere with this public network with parasitic emissions. Secondly, and most importantly, the communication protocol between a mobile terminal and a base station uses specific codings, including Gaussian Minimum Shift Keying type GMSK coding which means Gaussian Minimum Gaussian frequency shift agility. Such encodings require on reception a decoder of the same type for receiving and interpreting signals transmitted by a transmission modulator of the mobile terminal. This makes the accessory receiving device excessively expensive, such decoding requiring very complex signal processing means.
The patent application EP 0 830 044 presents such a system and proposes to solve the first problem, that is to say that of interference with the signals of the public network. However, this solution fails to solve the second problem, and therefore has the disadvantage of a complex system.
US5404391 discloses a mobile phone with simple accessory, which uses for pure mobile communication with the mobile phone, but which requires a specific modulator for communication with a base station and another modulator for communication with the accessory. .
In the invention, to solve this communication problem, it was desired to communicate with an accessory without however having to install a specific circuit in the receiving accessory to receive signals modulated according to a type of GMSK coding, nor having to install in the mobile terminal a parallel circuit for eliminating the functions of the GMSK encoder. In the invention, on the contrary, the GMSK type encoder will be used.

However, to avoid complication effects on the signal transmitted, we then arrange to feed the GMSK encoder with suites of bits whose translation, after coding and modulation, is expressed under the as a pure sinusoidal modulation of a carrier frequency to modulate.

We will show in the invention that we are then able to produce several specific bitstreams leading to several modulations by pure sine waves of the carrier frequency. By alternating such bitstreams specific, it can cause the sending of coded signals. With these signals coded, in the accessory, just make a simple receiver likely to detect the presence of a pure sinusoid and, where appropriate, measure the frequency of the modulation signal. We will show on the one hand that the equipment to achieve such a reception is more rustic, it is very cheap. On the other hand, by doing so we are able to solicit a accessory among many and thus to effectively transmit information at a rate which is not negligible since it may be of the order of or greater than 10 Kbits.

• le modulateur d'émission du terminal mobile module une deuxième porteuse située dans la gamme de fréquence normalisée,
• les deuxièmes informations sont transmises par une modulation en sinusoïde pure du signal de la deuxième porteuse.

The subject of the invention is therefore a method of communication between a mobile terminal and an accessory of this mobile terminal, the mobile terminal being able to exchange first information with a base station by modulating a first carrier located in a frequency range normalized by signals representative of the first information, with a transmission modulator, and the mobile terminal can additionally transmit second information to the accessory. This process is characterized in that, for transmissions of the second information to the accessory,

• the transmission modulator of the mobile terminal modulates a second carrier located in the standardized frequency range,
• the second information is transmitted by pure sine wave modulation of the second carrier signal.

• des premiers moyens pour l'échange de premières informations avec une station de base en coopération avec un modulateur d'émission modulant une première porteuse située dans une gamme de fréquence normalisée par des signaux représentatifs des premières informations, et
• des deuxièmes moyens pour transmettre des deuxièmes informations à un accessoire (2),

   Ce terminal se caractérise en ce que les deuxièmes moyens sont aptes à transmettre ces deuxièmes informations en coopération avec le modulateur d'émission, en modulant une deuxième porteuse située dans la gamme de fréquence normalisée, par des sinusoïdes pures.The invention also relates to a mobile terminal for implementing this terminal, a mobile terminal comprising:

• first means for exchanging first information with a base station in cooperation with a transmission modulator modulating a first carrier located in a frequency range normalized by signals representative of the first information, and
• second means for transmitting second information to an accessory (2),

This terminal is characterized in that the second means are able to transmit these second information in cooperation with the transmission modulator, by modulating a second carrier in the normalized frequency range, by pure sinusoids.

• Figure 1 : une représentation schématique d'un terminal mobile, d'une station de base et d'un accessoire utilisé pour mettre en oeuvre le procédé de l'invention ;
• Figure 2 : une représentation temporelle de signaux échangés entre le terminal mobile et la station de base d'une part, et le terminal mobile et l'accessoire d'autre part dans une application de type GSM-TDMA (Time Division Multiple Access, accès multiple à répartition dans le temps) ;
• Figure 3 : une représentation d'un modulateur classique d'un terminal mobile avec un perfectionnement de l'invention ;
• Figure 4 : une représentation d'un démodulateur à mettre en oeuvre dans l'accessoire ;
• Figure 5 : des représentations de trains de bits spécifiques à l'invention utilisés pour exciter un codeur GMSK.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are presented only as an indication and in no way limitative of the invention. The figures show:

• Figure 1: a schematic representation of a mobile terminal, a base station and an accessory used to implement the method of the invention;
• FIG. 2: a temporal representation of signals exchanged between the mobile terminal and the base station on the one hand, and the mobile terminal and the accessory on the other hand in a GSM-TDMA (Time Division Multiple Access, access-type application) time division multiple);
• Figure 3: a representation of a conventional modulator of a mobile terminal with an improvement of the invention;
• Figure 4: a representation of a demodulator to implement in the accessory;
• FIG. 5: representations of bitstreams specific to the invention used to excite a GMSK coder.

FIG. 1 shows a mobile terminal 1 that can be used to implement the communication method of the invention when it comes into contact with an accessory 2.
The accessory 2 comprises for example a headset microphone and / or a call alert buzzer.
It can be provided that the mobile terminal 1 comprises only the basic means, including those necessary for telecommunication, and the other means normally implemented in a mobile terminal are deported on one or more accessories. Thus, the microphone and speaker may be present only on the accessory 2 and not on the mobile terminal 1.

In a known manner, the mobile terminal 1 exchanges information, over the air 3, with a base station 4 of a public or private network mobile phone. The exchange of this information is done by modulating, by means of a transmission modulator contained in the mobile terminal 1, a carrier Fj located in a standardized frequency range. We know thus the useful frequency ranges of the different standards, GSM (range between 880 MHz and 960 MHz), DCS (useful range between 1710 MHz and 1880 MHz), PCS (useful range between 1850 MHz and 1990 MHz) and UMTS whose frequency is of the order of 2200 MHz. Range standardized includes the useful range plus overflows at the edges of useful range. The idea of the invention is, from this point of view, that if an emission 3 occurs in one of those normalized ranges of relationship between the mobile terminal 1 and the base station 4, the frequency of a wireless link 5 used by the mobile terminal to communicate with Accessory 2 will be located in the same standard frequency range. This way we avoid, by programs not originally planned, to make noise in standardized ranges reserved for other communications. In addition, choosing these frequency ranges, of course all the mobile terminal will be maintained as is. There will be nothing to change. Which also leads to the reduction of the price of the terminal-accessory set.

FIG. 2 shows, in the context of a GSM-TDMA type application, a mode of exchange of a mobile terminal with a base station on the one hand and with accessory 2 on the other. On the time diagram shown, the mobile terminal receives during a time window 6 RX signals transmitted on a carrier Fp by the base station 4. In a manner known, during a time window 7, later or earlier in the same frame 8, the mobile terminal is supposed to send TX signals to the base station 4. The RX and TX signals are speech signals, or digital data.

The power level of the signals that the mobile terminal 1 is likely to send to base station 4 may vary. This level depends on the mobile terminal away from the base station 4. This level is between a minimum level 9 and a maximum level of 10. In a manner known, the carrier frequency of the transmission of the mobile terminal in response will be Fj, evolving temporally according to a pre-established frequency plan. The Frequencies Fp and Fj are within the normalized range. However, standardized range, according to the standards, is separated into two bands: one first band is used for transmissions from the base station to the mobile terminal, and a second band is used for terminal transmissions mobile to the base station. In order not to disturb other mobile terminals that would be located near the mobile terminal 1, in its air relation 5 with its accessory 2, the mobile terminal 1 use a carrier frequency Fk in the band allocated to mobile terminal 1 transmissions to base station 4: the frequency range Fj.

In addition, preferably, the transmission level 11 of the mobile terminal in its relation 5 with the accessory 2 will be lower than the minimum level 9. This will prevent the base station 4 from being solicited by signals intended for the accessory 2. At the time of the call of the mobile terminal 1 by the base station 4, the latter can, during the time window 7 itself, transmit a signal at the frequency Fk to the accessory 2. Indeed at the moment of the call, the window 7 is not used by the mobile terminal 1 for communicate with the base station 4. Or if it is, it is with the expected frequency Fj different from Fk. Eventually, if the modulator of transmission of the mobile terminal is multi-carrier it can both converse with the base station 4 during the window 7, on the carrier frequency Fj while he will converse with the accessory 2 on the carrier frequency Fk. In these cases, Fk will be different from Fj.

It is quite possible, however, that the emissions 5 to of accessory 2 are located during time windows 12 and 13 different from the time window 6 and the time window 7. It is also possible of course that more than one time window during a frame 8 of eight windows is used by the mobile terminal 1 for conversing with the accessory 2. So on a frame of eight windows, up to six windows, except the reception window 6 and the transmission window 7, may be used to converse with accessory 2.

It will be noted that in the invention, the organization in time windows will naturally be implemented, without any particular difficulty, simply because the mobile terminal is already provided with a part of organs allowing the operation during time windows and secondly from a program in its operating system allowing operation during selected windows. Quite simply, in the case of conversation with accessory 2, the program will be modified so that, two or six windows can be used as part of the connection with accessory 2. It is clear that in doing so, nothing changes in the mobile terminal, if not the content of the program. This content additional program can be saved once and for all. He ... not causes an extra memory occupancy that minimum, and between very easily in the place still available in program memory of a mobile terminal.

Figure 3 shows in summary, what is currently best in the field of mobile terminal modulators, including multi-carrier modulators. A signal to be emitted, having previously undergone compression, redundancy, channel or other encodings, is available in digital form at the output of a generator 14. It's going to be spectrally synthesized. An encoder 15, in particular of the GMSK type, receives the bits of the signal to be transmitted and, according to previous bits of the same signal (in a simplified example, we will take 2 previous bit times), produces encoded signals, symbols, resulting from linearization of the modulation over a given period of time (in the 3-bit example). Coding could be different from a GMSK encoding. Anyway, a coding equivalent would be implemented leading to output signals from the modulator difficult to interpret. In the invention, it is taught search the bitstreams of the generator 14 whose coding by the encoder 15 causes modulation by a pure sinusoidal signal of the carrier resignation. In an example according to the GSM standard, the signal bits are delivered by the generator 14 at a frequency of 13/48 MHz (equal to substantially at 270 KHz). The encoder 15 delivers the symbols to this same pace. A conversion table 16 then delivers samples of instantaneous frequency corresponding to the symbols produced by the encoder 15.

A phase accumulator 17 connected to the conversion table 16, thus receives a signal proportional to the frequency. The accumulator 17 adds a sample received to its own content, and re-injects it all onto one of his two entrances. The accumulator 17 therefore produces a phase instantaneous evolving regularly. Rather than having at the exit of the accumulator of phases, of an instant phase that at the rate of generation of the signal bits, it is preferred to oversample the output of phase accumulator by making it work at a significantly higher speed fast, for example from 8 to 32 times its speed. In one example, the rate of oversampling will be 16. This means that the conversion table of symbols in frequency value and the phase accumulator are solicited to a rhythm of 16x13 / 48 = 13/3 MHz for example. The frequency value is normalized to correspond to a phase difference that is would produce during a period of oversampling.

Benefiting from an instantaneous phase, it is possible, by means of sine and cosine transformation tables 18 and 19, to produce signals corresponding to the instantaneous amplitudes of a modulating signal. It is enough then transform these instantaneous amplitude signals by analog digital converters 20 and 21 (CNAs) and inject them into mixers 22 and 23 for producing the signal to be transmitted. Mixers receive in quadrature by a phase-shifter 24 a carrier signal of a local oscillator 25. The signals produced by the mixers 22 and 23 are then mixed in a third mixer 26 also playing a role amplifier. The amplifier is connected to an aerial 27 to transmit the signal.

To obtain a carrier Fj programmable from a signal to a frequency around zero, it is necessary to cause a frequency jump by an adder 28. It is known to insert this adder 28 between the conversion table 16 and the phase accumulator 17, to be superimposed on each sampling period, the programmed carrier frequency Fj at the instantaneous modulation frequency. To make this addition, of course, the oversampling rate must be greater than the maximum frequency synthesized so as to avoid folds of spectra. In one example, the maximum synthesized frequency is 26 MHz. This maximum frequency corresponds to 64 bands of 200 KHz (ie 12.8 MHz) multiplied by two to meet the Nyquist criterion. We choose in this case an oversampling rate of 4, leading to a frequency of 104 MHz oversampling.

By doing so, one can transmit, with the aerial 27, signals to destination of the base station 4. Nevertheless, it is also possible to issue signals to the accessory 2. In this case, a signal representative of the frequency Fk is admitted at the input of the adder 28. According to the invention, the signal available on the overhead 27 will be a modulation by a pure sinusoid, or having at least one strong modulation spectral component by a pure sinusoid. Under these conditions, Figure 4, just place in the accessory 2 a very simple receiver. This will naturally include a aerial 29 in connection with a mixer 30 which receives a signal in from a local oscillator 31. The local oscillator 31 will be an oscillator stalled at a frequency Fk, corresponding to a predetermined frequency for sending signals to the accessory 2. At the output of the mixer 3 will be arranged a low-pass filter 32. The cutoff frequency of the filter 32 will be determined so that this filter can be used for a circuit 33 of envelope detection. The circuit 33 will include for example in a manner simple a diode in series 34 and a capacitor in parallel 35. The circuit 33 is a rectifier circuit delivering at its output 36 a state one or zero depending on whether filter 32 will let pass or will not pass products of demodulation from the mixer 30.

Figure 5 shows how to produce modulation signals by a pure sinusoid of a carrier frequency in the modulator of the figure 3. In one example, the generator 14 produces an alternating succession of and zeros or a succession of zeros. In this case, we can show that at the output of the mixer 26 there is a carrier frequency Fk modulated by a pure sinusoid at 67 KHz. Otherwise, if the generator 14 produces alternating successions of couples of one and couples of zero, the Frequency Fk will be modulated by a pure frequency of 25 KHz. In the first case, depending on whether we have been charged by the generator 14 a suite alternating ones or zeros or only zeros, the available signal at the output of the mixer 26 will be a signal at +67.7 KHz or -67.7 KHz. In practice the resulting phase inversion also depends on the state of the phase encoder 15 at the moment when it receives the signals of the generator 14. If an envelope detector is adopted as the reception in accessory 2, the distinction between +67.7 KHz and -67.7 KHz may have little interest. By choosing a different receiver one can use this difference. In particular, it suffices to have a local oscillator 31 producing a signal at Fk - 67.7 KHz. In this case the signal demodulated in baseband oscillates at either 135.4 KHz or 0.4 MHz depending on the signal issued. It can also be discriminated by an envelope detector and a adapted filter.

As part of the GSM-TDMA example, in a time window of 577 microseconds with 156 bits, the duration of a bit-symbol is the order of 3.7 microseconds. Given the presence of the filter 32, especially when the signal modulating by a pure sinusoid is a signal to 25 KHz, it will be necessary to emit the modulated carrier during at least 40 microseconds for the filter 32 to receive a complete alternation of the signal at 25 KHz. As a precautionary measure, a longer duration of the order of 70 to 80 microseconds. In practice, we will choose to constitute with the generator 14 blocks of 20 symbols of this generator whose translation in terms of modulation on the signal transmitted by the aerial 27 will be a modulation by a signal evolving in a pure sinusoid.

In practice, during a time window we will not be able to transmit that seven blocks of 20 symbols so seven bits of useful information. We can choose shorter emission times, including a number encoder symbol less than 20, to increase the flow rate of transmission of the channel thus constituted. In this case, however, reception may to be of less good quality. On the contrary, we can focus on quality at detriment of flow. In this case the symbol blocks will have more than 20 symbols.

To receive signals at 25 KHz or 67 KHz, so with two separate frequencies, it is possible to double the filter 32 and the detector envelope 33 into a filter 37 and an envelope detector 38. In this case, one of the two filters 32 and 37 is provided to cut the frequencies located in intermediate position between the two sine wave modulation frequencies pure restraint. For example, the low-pass filter 32 will have a frequency of cutoff of 45 KHz while the low-pass filter 37 will have a frequency of cutoff below 15 KHz. This filter 32 will then let the signals go to 25 KHz but will block the signals at 67 KHz. If necessary, we can provide high-pass filters instead of low-pass filters. We can also provide a double alternation recovery instead of one-time alternation (which allows to increase the flow of the channel) or a multiplication filters 32, 37 and others and plan to send several pure sinusoids different.

It is also conceivable in the latter case, given a detection threshold to be set for the measurement of signals output from detectors such that 33 and 38, to provide to send a complex signal by the encoder 14. This complex signal is such that several detectors such as 33 and 38 can be solicited at the same time, but not others. By schematizing, we could provide that the signal modulating the carrier Fk is or is not a signal to a combined frequency of 25 KHz and 67 KHz.

It remains in all cases that the encoder 15 GMSK type, whose explanations relating to Figure 3 show that it is difficult to eliminate in the transmission chain. In reception, a simple set of filters such as 32 and 37 will still allow the accessory 2 to receive the information intended for it.
By doing so, by transmitting 7 bits for 577 microseconds, a bit rate of the order of 10 kbit / s is obtained. If several windows of the same frame are used, the flow can be much larger.

It is possible to obtain a variation of the modulation of the signal available at the output of the modulator 26 other than by modifying a block from symbols to another, the signals output by the signal generator 14 and / or the encoder 15. In this case, it would be preferable to feed the encoder 15 always with the same sequence, one of those indicated above, or another, which would result in the air carrier 27 transmitting a carrier modulated by a single signal at a pure sinusoidal frequency. In this case, for transmit information, we slightly modify the local oscillator 25 to work as follows.

Oscillator 25 could thus be a frequency oscillator intermediate (of the order of 100 MHz) or an oscillator at a frequency of transition (equal to the transmission frequency Fj plus or minus the frequency intermediate). Such a local oscillator 25 is normally stabilized from of a quartz as follows. A quartz circuit 39 produces a signal at 13 MHz. A divider 40 located at the output of divider 39 divides this signal by 65 to produce a signal at 200 KHz. The frequency of 200 KHz is typically the modulation width of a transmission frequency Fj (or Fk) by the terminal mobile. It is also the gap that separates two carrier frequencies Fj and Fj ' related. The signal delivered by the divider 40 is then introduced into a comparator 41 which controls the voltage oscillator 25. A divider 42 takes the signal at the output of the local oscillator 25, divides it by a coefficient chosen, and reinjects it on another input of the comparator 41. Such a circuit of feedback has the effect that the signal delivered by the oscillator 25 is a multiple, by the chosen coefficient of the divider 41, the bandwidth (200 KHz) of the feedback loop. When such a system is set, and when the signal generator 14 produces bitstreams like those indicated in FIG. 5, the modulation of the carrier Fk is constant.

Such constant modulation, of course, only transmits imperfect information related only to its existence or absence. If we stood there, it would produce the following result as soon as a mobile terminal would like to question an accessory of its own, other accessories attached to other mobile terminals, manufactured in the same way, would also be solicited. Such binary information is therefore not not enough.

In the invention it is provided, rather than changing in this case the trains of symbols of the generator 14, to modulate the voltage control of the local oscillator 25. In practice, this may return to have a circuit adder 43 between the output of the comparator 41 and the control input of the oscillator 25 on the one hand and between the oscillator 25 and a converter 44. The converter 44 delivers a voltage corresponding to a control signal transmitted to it by a bus 45. The bus 45 is in relation with a microprocessor system of the terminal mobile. This microprocessor system is suitable for placing on the bus 45 to converter destination 44 a binary state of n. This binary state generates an addition, in the regulator chain of the oscillator 25 of a error voltage able to shift the setting of the local oscillator 25.

In practice, in every mobile terminal there is a chain of regulator comprising the comparator 41, the local oscillator 25 and the divider 42. In some all-digital montages, it may even be possible to switch from the adder 43 and the converter 44. Indeed, the divider 40 and / or the divider 42 may be designed in the form of up-down counters by 65 (or others). We can then use the available binary state on the bus 45 to preset, before counting down, the counter 40 and / or the down-counter 42. They are preset in a different counting state from scratch. In this case, the signal available at the output of the oscillator 25 will be offset in frequency. This frequency shift is equivalent, approximately, to frequency modulation of the carrier. In any case, it can be received very simply in the circuit of Figure 4.

By doing so, we make sure that the modulation frequency available in transmission is a chosen frequency, for example 67 KHz, modulated itself by the binary states delivered by the bus 45. Either these states binaries are zero in which case the signal received in the receiver 29-38 is a signal at a single frequency of 67 KHz. Either these binary states are different from zero and evolve over time. Oscillator 25 is then altered in operation and the signal resulting from the modulation at 67 KHz is shifted to one or more other values. These other signals can be detected with other filters as explained above. Either the offset is such that the signal sent out completely from the receiving band. In which case, there is absence signal at 67 KHz. In this case the modulation is all or nothing type.

As much in the previous case it took 20 symbols to the encoder 15 for that at the time of reception we can detect a signal at 25 KHz, as much a duration corresponding to 10 symbols will be sufficient in the case where the modulating frequency is 67 KHz. In this case, the flow can even go up to 16 bits during a time window 12, 7, or 13 of 577 microseconds. With such a distribution, the microprocessor system of the mobile terminal 1 must put binary states on the bus 45 with a rate of sixteen states per time window. It will be noted that with this last solution the flow is higher without needing another channel 37, 38 of envelope detector.

Rather than using a frequency Fk located in the useful band of the normalized range, we may prefer to be slightly above or below or, strictly speaking, between two useful bands of this standardized range. By example in the context of the GSM for which the useful band is 880-960 MHz, it can be expected that the frequency Fk will be 870 MHz or up to 850 MHz. In this case, the carrier frequency Fk is chosen at a frequency located in the normalized range, out of the useful band, but within 5% of the edge of the useful band.

For the determination of the frequency Fk usable with the oscillator local 31, provision can be made to match the accessory 2 with the mobile terminal in factory. The accessory 2 is thus equipped with a local oscillator 31. The local oscillator 31 does not need to be adjustable. Just measure how often, in the standardized emission range retained, it is likely to produce. In these conditions with the mobile terminal 1, given that the latter has a significant exploration potential of the entire emission range that it is likely to have to ensure, we can choose the frequencies Fj of this mobile terminal which, modulated by a signal at a pure frequency as said above can lead filters 32 and 37 to discriminate the presence of a signal at this pure frequency. In other words, we measure the frequency Fk natural oscillator 31, and we choose this frequency Fk as frequency exchange. In this case, the adder 28 receives from the system to microprocessor of the mobile terminal signals corresponding to Fk when to communicate with the accessory.

Claims (18)

1. Communication method between a mobile terminal (1) and an accessory (2) of this mobile terminal, said mobile terminal being able to exchange (3) first data with a base station (4) by modulating a first carrier (Fj) located in a frequency range standardized by signals representative of said first data, using a transmission modulator (14-28), and said mobile terminal also being able to transmit (5) second data to said accessory, and for the transmission of second data to said accessory:

   said transmission modulator of said mobile terminal modulates a second carrier (Fk) located in a standardized frequency range,

   said second data are transmitted by pure sine wave modulation of the signal of said second carrier.
2. Method as in claim 1, characterized in that the transmission modulator uses modulation of GMSK type (15).
3. Method as in either of claims 1 to 2, characterized in that said second carrier has a frequency equal to that of said first carrier.
4. Method as in either of claims 1 to 3, characterized in that said accessory is a vibrator.
5. Method as in any of claims 1 to 3, characterized in that said accessory is of head microphone type.
6. Method as in any of claims 1 to 5, characterized in that said second data are transmitted by two pure sine wave modulations of the signal of the second carrier.
7. Method as in any of claims 1 to 6, characterized in that said second data are received in said accessory by filtering with a low-pass filter (32) the signals transmitted after their demodulation, and by subjecting the filtered signal to envelope detection (33).
8. Method as in any of claims 1 to 7, characterized in that a central frequency (Fk) of a local oscillator (31) of said accessory is factory tuned with one of the possible frequencies in said mobile terminal for the first carrier (Fj).
9. Method as in any of claims 1 to 8, characterized in that as frequency of said second carrier a frequency is chosen that is located in the standardized range, outside an effective band, and at less than five per cent outside the effective band.
10. Method as in any of claims 1 to 9, characterized in that, for modulation, the frequency of a local oscillator (25) is shifted by regulating (43-45) its regulating circuit (41-42) by counter-reaction.
11. Mobile terminal (1) comprising

    first means for the exchange (3) of first data with a base station (4) in cooperation with a transmission modulator (14-28) modulating a first carrier (Fj) located in a frequency range standardized by signals representative of said first data, and

    second means for transmitting second data to an accessory (2)

    and said second means are able to transmit said second data in cooperation with said transmission modulator by modulating a second carrier (Fk), located in the standardized frequency range, by pure sine waves.
12. Mobile terminal as in the preceding claim, characterized in that said transmission modulator is able to implement modulation of GMSK type.
13. Mobile terminal as in either of claims 11 and 12, characterized in that said first carrier has a frequency equal to said second carrier.
14. Mobile terminal as in any of claims 11 to 13, characterized in that said second means are able to transmit said second data to a vibrator.
15. Mobile terminal as in any of claims 11 to 13, characterized in that said second means are able to transmit said second data to a head microphone.
16. Mobile terminal as in any of claims 11 to 13, characterized in that said second means are able to transmit said second data to a vibrator.
17. Mobile terminal as in any of claims 11 to 16, characterized in that said second means are able to conduct two pure sine wave modulations of said second carrier.
18. Mobile terminal as in any of claims 11 to 17, characterized in that said second means are designed to operate with a frequency of said second frequency located in the standardized range, outside an effective band, and at less than five per cent outside the effective band.

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